AM and PM are abbreviations used to denote time in the 12-hour clock system.
AM stands for “Ante Meridiem,” which is Latin for “before midday.” It refers to the time from midnight (12:00 AM) to just before noon (11:59 AM).
PM stands for “Post Meridiem,” which is Latin for “after midday.” It refers to the time from noon (12:00 PM) to just before midnight (11:59 PM).